A majority of the headlights manufactured today are constructed of plastic, namely polycarbonate. Polycarbonate is lightweight, has excellent impact resistance and clarity, and is easy to mold into various shapes. However, polycarbonate laminates are known to discolor during prolonged exposure to the elements. The discoloration is typically surface located if treated before structural integrity becomes an issue. However, even discoloration of the surface causes the clarity of the plastic to degrade causing a dramatic reduction in light transfer through the plastic and forming an aesthetically unpleasing appearance. While plastics typically include an ultra-violet light inhibitor to reduce the rate of structural breakdown, inhibitors lose their ability to continue to protect the material over time with the laminate coating being the first to suffer.
While the discoloration of the lens is visually unpleasing, a safety concern arises in the operation of a vehicle having discolored headlight lens at night. On-coming traffic may believe the vehicle is farther away if the headlights are dim. The operator of the vehicle will have reduced illumination which can endanger the operator and their occupants should the speed of the vehicle be increased beyond the range of headlight illumination.
Replacement of the lens is possible, however, it is an expense that few vehicle owners are willing to spend. Another option is restoration of the lens, which is possible if the restoration is performed before structural degradation of the plastic has occurred.
To address the loss in clarity and associated reduction in safety, numerous treatments to the plastic have been introduced to the market. Basic plastic restoration consists of sanding off the oxidation and then coating the lens with a material. Unfortunately the known plastic restorations are either temporary, difficult to apply, or result in a treatment that accelerates the problem.
U.S. Pat. No. 4,954,591 discloses polymerizable and cross-linkable, radiation curable coating composition designed for deposition as a tintable coating. The formulation is a mixture including: (a) 25-94% by weight of a polyfunctional acrylate or methacrylate monomer having at least three acrylate functional groups per molecule or a mixture of such monomers; (b) 3-50% by weight of a monomer selected from N-vinyl derivatives of linear or cyclic secondary amides, tetrahydrofurfuryl acrylate or methacrylate, N,N-di(lower alkyl) acrylamide ethylenically unsaturated monosilane, or a mixture of such monomers; and (c) 3-40% by weight of an ethylenically unsaturated monomer having a Tg less than 80 degrees C. or 3-30% of an ethylenically unsaturated copolymer with a Tg less than 100 degrees C. Ultra-violet radiation is supplied by a 6-inch 200 watt/inch mercury lamp.
U.S. Patent Appl. No. 2001/0008691 discloses a UV curable resin composition for coating the surface of a poly-carbonate resin molded article such as a lamp cover for automobiles. In the UV curable resin composition for coating (a) 10-70 wt. % of a mono- or bi-functional monomer having a molecular weight of 130-700, and having ether bond and one or two acryloyloxy groups per molecule, (b) 5-60 wt. % of an aliphatic urethane acrylate oligomer, (c) 10-30 wt. % of a methyl methacrylate polymer having a molecular weight of 10000 to 200000, as necessary, and (d) 5-50 wt. % of a polyfunctional monomer having a weight of 250-700 and having three or more acryloyloxy groups per molecule, mixed 2-10 parts by weight of a photopolymerization initiator, and 2-20 parts by weight of a UV absorber.
U.S Patent Appl. No. 2009/0148606 discloses a restoration kit for the plastic light cover on an automobile or other plastic surface. The kits and methods utilize polishing compositions having particles selected so as to polish a plastic surface, and a UV protective composition such as an acrylic polymer that forms a UV protective coating. The polishing compositions may include agglomerated abrasive particles dispersed in a liquid or gel carrier that progressively break down in size when exposed to oxygen and mechanical pressuring during polishing.
U.S. Pat. No. 6,984,612 discloses an automotive headlight restorer and cleaner which removes oxidation. The method of manufacture consists of an industrial degreasing compound, a mixture of about 53% mineral spirits, 3% butanol, and gloss spar varnish and/or acrylic urethane. One solution is used on lenses with heavy oxidation and severe damage and the other solutions are for lenses with less severe oxidation and damage.
U.S. Pat. No. 7,045,001 discloses a kit and method to resurface and restore plastic material, and in particular, the plastic lens covers over the headlights of an automobile. The kit includes a pretreatment formulation, a resurfacing formulation, and a restoration formulation. The restoration formula includes an aqueous polymer such as methyl methacrylate and ethyl methacrylate.
U.S. Pat. No. 7,163,446 discloses a method of restoring a discolored automobile headlight lens by first sanding the outer surface of the lens with successively finer grit wet sanding disks until a smooth surface is achieved exhibiting no discoloration. The surface is then polished with an aqueous paste abrasive polish containing aluminum oxide abrasive particles. The outer surface of the lens is then sprayed with a film forming aqueous polymer dispersion containing an ultraviolet protectant. The sealer comprises of acrylic urethane copolymers, Hindered Amine Light Stabilizers, benzotriazole UV light absorbers, 1-methyl-2-pyrrolidone, and dipropylene glycol monomethyl ether.
U.S. Pat. No. 7,404,988 discloses refinishing an exterior automotive lens having a damaged exterior surface in situ using a continuous movement and oscillating motion, with first, a 320 grit sanding disc, next a 600 grit sanding disc, and finally a 1500 grit sanding pad while flushing the surface with water to prevent melting of the surface. The surface is then buffed with a polishing compound until a high gloss is achieved. Finally, the surface is coated with a transparent ultraviolet hardenable coating material, and hardened by exposure to an ultraviolet light source. The claim is limited to the use of an oscillator device having a rotational oscillating motion.
U.S. Pat. No. 7,713,628 discloses a cured coating or molded article prepared from a composition comprising an actinic-radiation curing polymer, wherein the composition is cured with actinic radiation at a temperature of at most 150 degree C. to form the cured coating or molded article; wherein the cured coating or molded article has a thickness of at least about 0.5 mm and a hardness of about Shore A 90 to about Shore D 90.
U.S. Pat. No. 5,443,604 discloses a polishing compound for plastic surfaces. The compound contains by weight approximately 4 to 17 parts. At least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size.
U.S. Pat. No. 5,633,049 discloses an acid-resistant and abrasion resistant protective coating for thermoplastic transparencies, particularly aircraft transparencies. The coating is prepared from a silica-free protective coating precursor composition comprising a multifunctional ethylenically unsaturated ester of acrylic acid, a multifunctional ethylenically unsaturated ester of methacrylic acid, or a combination thereof; and an acrylamide.
U.S. Pat. No. 6,244,707 discloses contact lenses, intraocular lenses and transparent plastic with enhanced UV blocking to meet ANSI Class 1 specifications including effective amounts of two different UV absorbing compounds. One UV absorber is a benzotriazole derivative, and the other UV absorber is a benzophenone derivative. The lenses are made from a polymer that incorporates both of these UV absorbers.
U.S. Pat. No. 6,306,502 discloses a coating composition forming an abrasion resistant coating comprising an ultraviolet-curable silicone prepared by chemically modifying particulate colloidal silica with a specific compound, a monomer mixture comprising a (meth) acrylate having a specific isocyanate skeleton and a urethane poly(meth)acrylate having an alicyclic skeleton, and a photo-polymerization initiator.
U.S. Pat. No. 6,846,567 discloses a surface-protected plastic composite material comprising a transparent plastic, a coating layer as a first layer stacked on the transparent plastic and a thermally cured coating layer as a second layer stacked on the first layer, the coating layer (I) being formed of a resin composition containing at least 50% by weight, based on the resin content thereof, of an acrylic resin which is an acrylic resin containing at least 50 mol % of recurring unit based on an alkyl methacrylate, the thermally cured coating layer (II) being made of an organosiloxane resin formed from the following components a, b and c, (A) colloidal silica (component a), (B) a hydrolysis condensate (component b) of a trialkoxysilane, (C) a hydrolysis condensate (component c) of a tetraalkoxysilane, the organosiloxane resin containing 5 to 45% by weight of the component a, 50 to 80% by weight of the component b, and 2 to 30% by weight of the component c, and use of the composite material as a window glass.
U.S. Pat. No. 7,793,786 discloses a method to coat vehicular plastics with an epoxy coating. One embodiment includes a system that may be used to remove damaged plastic and any existing hard coat material, such as silicone, from the surface of a vehicular plastic. Such embodiments may also include the epoxy coating and tools necessary for applying the epoxy. Another embodiment discloses a process for preparing and sealing a vehicular plastic with an epoxy coating.
U.S. Patent Appl. No. 2007/0133098 discloses the Headlight Detailer (HLD) as a three part process utilizing specific compounds and a procedure for the purpose of detailing automobile headlights and restoring the functionality of the headlight lens. The first part of the process consists of using readily available glass cleaner applied to the headlight lens for initial cleaning. The second step in the process is applying an ammonia and silicone based solution for the purposes of enhanced cleaning and surface preparation. The third and final step in the process includes the application of a wax sealer containing a solution for regenerating the hardened acrylic resin lens surface coating and UV protection.
U.S. Patent Appl. No. 2009/0042761 discloses a solution for cleaning plastic headlight covers that includes an oily acid, a surfactant, a citrus turpene and hard nanoparticles of sapphire and diamond. Principal ingredients are carried by commercial windshield cleaning solution or in water.
U.S. Patent Appl. No. 2009/0176678 discloses a cleaning solution for plastic headlight covers which includes a saturation of crystallizable salts, such as ammonium sulfate or urea; an organic solvent, such as turpene, glycol ether or alkyl alcohol; a buffered acid to maintain pH between 3.0 and 5.5, such as citric acid, oxalic acid, sodium bisulfate, or boric acid; alumina nanoparticles of 0.05 micron size and other submicron sizes; as well as a sequestering (chelating) agent, surfactant, and hydrophilic combiner; all in an aqueous solution. The cleaning solution effectively removes the mineral solids from the crazed surface of a plastic headlight cover that form a base for accumulating organic residue and road grime. No abrasive scouring or recoating of the surface with an acrylic sealant is required.